Many applications in industry require the use of an ultraviolet (UV) light emitting lamp assembly. For example, ultraviolet light is often used to cure various UV curable materials, such as adhesives used to assemble products or packaging, and inks used on such products and packaging. UV lamp assemblies may be microwave powered or electrode powered and typically include a reflector which partially surrounds an elongate lamp bulb for reflecting the ultraviolet radiation emitted by the bulb onto the substrate, such as products or product packaging. The reflector commonly has a reflective surface which is elliptical or parabolic in shape and the lamp bulb is mounted along the symmetrical centerline and adjacent the apex of the reflector. The reflector increases the intensity of radiation received by the UV curable material and, therefore, the penetration of the radiation into the curable material.
Often, it is desirable to shutter the lamp on and off during a manufacturing process. It may be desirable to only irradiate a product on an assembly line for a discreet, relatively short period of time. Turning the power to the lamp on and off is one possible way to achieve the desired on/off effect, but is not practical in many situations. For example, the time period necessary to power up and power down may be too long for a high productivity environment. Also, constantly powering a lamp on and off can waste energy and shorten bulb life. As a practical alternative, mechanical shutters have been developed for selectively opening and closing a radiation emission opening of a lamp assembly while the lamp power remains on. Thus, the shutters substantially prevent the emission of radiation when closed but quickly permit full irradiation immediately upon being opened. This quickens the cycle time and therefore increases productivity.
One challenge faced with mechanical shutter systems is cooling the lamp bulb when the shutters are in the closed position. Normally, air flow is generated past the lamp bulb and freely escapes from the lamp assembly taking heat with it. When shutters are used, and they are closed, this generally restricts the air flow and allows excessive heat to build up around the lamp bulb which can harm the bulb and shorten its life. Various lamp assemblies use reflective panels to form the reflector in segments. In some lamp assemblies, two panels move together and apart in a clamshell arrangement to shutter light in a closed position and reflect light in an open position. Other lamp assemblies may add stationary reflector panels in addition to the movable panels depending on the desired effects. Cooling this type of lamp assembly has typically involved when using a so-called negative cooling system in which cooling air is drawn past the lamp bulb through a slot at the top of the reflector. In positively cooled lamps, air jets are directed at the bulb through slots in the reflector panels at various levels and in proper proportion to effectively cool upper and lower portions of the bulb. This is unlike the negatively cooled lamps which generally have a slot only at the top of the reflector.
Air cooled lamp assemblies using a multi-paneled reflector configuration require multiple long narrow panels of thin, highly polished aluminum. Without support, these thin panels can easily overheat and warp from the heat of the bulb. It is common to support the thin aluminum reflector panels with an extrusion formed to the desired profile. This works well for the outer reflector panels, but not as well for the center section. In order to cool the bulb, this center section or panel is perforated with a complicated pattern of holes. Therefore, using an extrusion to support this center panel would likewise require that the extrusion be drilled with the complicated hole pattern. This would lead to higher costs of manufacture. Moreover, thicker aluminum in which holes can be punched or otherwise formed prior to bending to the necessary reflective surface is not available in a highly polished, mirror finish.
Finally, due to the complexity of existing shutter mechanisms, the reflector panels in existing designs are difficult to replace as they require disassembly of the lamp head.
For these and other reasons, it would be desirable to provide an apparatus and method which enables more effective positive cooling of a lamp bulb, easier assembly and disassembly of the reflector panels, and less propensity for reflector movement or warpage.